A check constraint is used to define a range of values that are accepted by a column. It uses a logical expression to determine the acceptable values. チェック制約 can be defined on table level (i.e., several columns of a table are checked in the expression) or on a single column. Multiple チェック制約 can be applied to a single column.
チェック制約 on table level are shown with an アイコン when you expand the チェック制約 section of a table design. They are displayed together with the expression(s) that are used to validate the table.
チェック制約 on table level can be renamed and their expressions can be modified directly in the table design.
A check constraint on column level is indicated by the check column アイコン being displayed with the column the check constraint is defined for in the Columns section of the table design. Please note that this アイコン is not displayed if either a primary key, 一意キー, or 外部キー is defined for this column, or if the column is of type XML, since all these qualities are of a higher priority and their corresponding アイコン will be displayed with the column.
You can edit the expression in プロパティウィンドウ. To rename a check constraint on column level, right-click the constraint in the オンラインブラウザー and select Rename をコンテキストメニューから選択します。
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